The next beta version of redsn0w that is Redsn0w 0.9.7b4 will be for those who are having problem with the usbmuxd. Most probably usbmuxd will be integrated inside Redsn0w 0.9.7b4. After that the dev team will be releasing Redsn0w Redsn0w 0.9.7 for untethered iOS 4.2.1 jailbreak for windows. This has been confirmed on redsn0w testers Twitter account. Check out the conversation:

tman15555: @redsn0w_testers when will the version that incorporates usbmuxd be realeased? I keep on getting stuck on installing bundles

redsn0w_testers: @tman15555 that version is next…and if that’s successful, we should be able to expand to Windows testers after that